Fiber for artificial turf

ABSTRACT

A fiber for artificial turf is of the type of monofilament fibers utilized in the manufacturing of artificial turf carpets and which are obtained by extrusion with polyolefins, in polyethylene or another material. The fiber forming the carpets for artificial turf includes a flat rectangular general cross section with its shorter sides rounded. A central part of one of the longer faces of the fiber includes a curved-convex projection, and its other longer face includes a pair of curved-convex projections in a symmetrical position with respect to its central axis, with which a fiber is obtained for artificial turf with high resilience which facilitates its recovery against successive occasional or temporary loads, maintaining its original appearance for a longer time.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 National Phase of PCT/IB2010/052761 filed onJune 18, 2010, and published in English on Mar. 10, 2011, asInternational Publication No. WO 2011/027235 A1, which claims priorityto Spanish Patent Application No. P200930645 filed on Sep. 3, 2009, theentire disclosures of which are incorporated herein by reference.

OBJECT OF THE INVENTION

The following invention, according to what is expressed in the statementof the present specification, relates to a fiber for artificial turf,being of the type of fibers utilized in the manufacturing of artificialturf carpets, by weaving the fibers, such that the essential object isto obtain a fiber with some resilient characteristics which make itrecover its vertical position after being compressed, occasionally ortemporarily, maintaining its original appearance for a long time.

For that purpose, the extruded monofilament fiber manufactured withpolyolefins in polyethylene, has a certain cross section, and the heightof the fibers forming the turf carpets present a certain length.

In this manner, the fibers forming the artificial turf carpet areallowed to recover their vertical position after being subjected tosuccessive loads.

FIELD OF APPLICATION

In the present specification, a fiber for artificial turf is described,of special application in manufacturing artificial fiber carpets forturf in the installation of fields for different sports, such as soccer,golf, rugby, or hockey.

In the same way, the fiber for artificial turf is equally applied toother uses, such as gardens, access roads, or decoration.

BACKGROUND OF THE INVENTION

As it is known, each day there are more organizations and sports clubsopting to provide their installations, with playing fields for differentsports, with artificial turf as an alternative to natural grass turfsince they require less maintenance and to offer a sensation similar tothe one of natural grass turf and to present improvements, such as, anartificial turf field can be used all year round, and the natural grassturf fields by requiring a recovery period in which they cannot be used.These artificial turf carpets are manufactured by weaving the artificialfibers.

On the other hand, with the object to obtain artificial turf carpetswith fibers that maintain their characteristics over time, themonofilament fibers should have high resilience which makes them recovertheir vertical position after having been occasionally or temporarilycompressed over time, preventing the fibers staying tilted over theground.

In this manner, it has been attempted to obtain fibers made of differentmaterials and sections with the object to provide them with highresilience, being able to consider the patent documents U.S. Pat. No.6,432,505; EP 1837423, and PCT WO2005/005731.

In this way, in the American patent U.S. Pat. No. 6,432,505, a syntheticturf is described having a substrate and a plurality of turf filamentsmade of synthetic polymer anchored to the substrate, said filamentshaving a diamond-shaped cross section, with a longitudinal axis alongfrom one end to another end, and a lateral axis located in the middle,so that the thickness of the filament gradually decreases from saidlateral axis, substantially, symmetrically and smoothly over thelongitudinal axis toward each end.

In the European patent EP 1837423, a synthetic turf is describedcomprising a turf carpet and some knots projecting therefrom, the knotscomprise individual filament strands and at least one shredded strandand, at least, a number of said strands consists essentially of amixture of high density polyethylene and low density linearpolyethylene.

In the patent PCT WO2005/005731, an artificial turf filament isdescribed wherein the filament has, in cross section, a central area andtwo wing areas in the opposite sides of said central area, and with adivergent orientation, such that an outward protruding head is formed atone side of the divergent areas of the central area, and at the far sidefrom the divergent areas, the central area, has a face which isessentially aligned in the place of said central area and which ismerged to the adjacent faces of each wing area.

SUMMARY OF THE INVENTION

In the present specification, a fiber for artificial turf is described,being of the type of monofilament fibers utilized in the manufacturingof artificial turf carpets, by weaving the fibers and which are obtainedby extrusion in polyethylene or another material, such that the fiberfor artificial turf presents a flat rectangular cross section with itsshorter sides rounded, in the central part of one of its longer facesbeing provided with a curved-convex projection, and in its other longerface is provided with a pair of projections, equally curved-convex, in asymmetrical position with respect to its central axis.

In a preferred embodiment, the fiber for artificial turf has a width ofapproximately 1400 μm.

In the same way, in a preferred implementation the fibers for artificialturf which form the carpets have a height of approximately 60 mm.

The thickness of the fiber for artificial turf in the central part ofthe curved-convex projections is the same for all of them, such that ina preferred implementation the thickness of the fiber for artificialturf in the central part of the curved-convex projections is ofapproximately 270 μm.

For supplementing the description to be carried out next, and with theobject to aid to a better understanding of the characteristics of theinvention, a set of drawings is attached to the present specification,with figures where the most characteristic details of the invention aredepicted in an illustrative but not limitative manner.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1. Shows a perspective view of a segment of a fiber for artificialturf, being able to observe the cross section thereof.

FIG. 2. Shows a detailed perspective view of some weaved fibers formingthe corresponding carpet for artificial turf.

FIG. 3. Shows a results table of the recovery index of the fibers, withdifferent cross sections, to be analyzed, with a height of 60 mm,according to the elapsed time of 1, 30 and 240 minutes from its releasefrom a compressive load.

FIG. 4. Shows an evolution table of the fibers in their recovery overtime of 1, 30 and 240 minutes after their release from a compressiveload, according to the recovery index of the analyzed fibers with aheight of 60 mm.

FIG. 5.—Shows a classification table of the analyzed fibers according toa height of 60 mm, according to the elapsed time of 1, 30 and 240minutes, after their release from a compressive load.

DETAILED DESCRIPTION

Given that the resilience of the fibers forming the carpets forartificial turf is affected by both their section and the height of thefibers forming them, with the object to obtain a fiber for artificialturf with high resilience which facilitates its recovery againstsuccessive occasional or temporary loads and maintains its originalappearance, a series of samples of fibers of different sections havebeen analyzed in order to obtain that fiber presenting higherresilience.

In this way, taking into account that both the height of the fibersforming the carpets for artificial turf and its section affect therecovery thereof, i.e. their resilience and utilizing the methoddescribed in the Patent of Invention P200930107 wherein a method fordetermining the recovery grade in artificial fiber carpets is described,an analysis has been carried out in order to assess the recovery offibers with different sections, for which it determines the recoveryindex as well as the recovery rate, such that this parameter points outthe speed at which a material recovers after being released from a load.

From these premises, four samples of artificial turf carpets have beenanalyzed, with fibers of different sections being manufactured frommonofilament extruded polyethylene, and the fibers forming the carpetshave a height of 60 mm, one of the samples being the fiber object of theinvention with a certain section which confers it high resilience.

In this way, the section of the fiber object of the invention has beensubjected to an analysis together with three more samples of differentsections, so that the cross section of the fiber 1 object of theinvention (corresponding to the sample of section 3) presents a flatrectangular general shape with its shorter sides rounded, in the centralpart of one of its longer faces being provided with a curved-convexprojection 2, and in its other longer face is provided with a pair ofcurved-convex projections 3 in a symmetrical position with respect toits central axis.

In this manner, the special section of the sample 3 based on thecurved-convex projections of its longer faces confer it with highresilience, in which the height of the fiber forming the artificial turfcarpets collaborates.

Moreover, in a preferred implementation of the fiber 1 for formingartificial turf carpets, it has a width “D” of approximately 1400 μm.

On the other hand, the thickness “d” of the fiber for artificial turf inthe central part of the curved-convex projections is the same in all ofthem, such that in a preferred implementation is of approximately 270μm.

In this way, as observed in FIG. 2 of the designs, fibers 1 forming theweaved bundles of the artificial turf carpet, will have a heightpreferably of 60 mm, although, logically, the height could be anotherone.

As in the cited Spanish patent P200930107, the method is specified basedon applying to the samples a constant compressive load of 1400 kg during72 hours, such that, once said time is elapsed, the load is released andimages of the same zone are captured after 1, 30 and 240 minutes. Beforeapplying the compressive load, an image has also been taken in order toknow and define the total area occupied by the fibers, this valuecorresponding to 100% of the fibers in their state of equilibrium.

The captured images are analyzed for each one of the times and the areaoccupied by the fibers is calculated, assigning 100% recovery to theinitial area occupied by the fibers before applying the load, such thatcalculating the recovery index is carried out applying the followingratio

${{Recovery}\mspace{14mu} {index}\mspace{14mu} (\%)},{I_{t} = {\frac{{Area}\mspace{14mu} {after}\mspace{14mu} {releasing}\mspace{14mu} {load}\mspace{14mu} \left( {mm}^{2} \right)}{{Area}\mspace{14mu} {without}\mspace{14mu} {load}\mspace{14mu} \left( {mm}^{2} \right)} \times 100}}$

In this way, applying the described methodology, the results of therecovery index have been obtained for the carpets formed of some fiberswith a height of 60 mm, shown in the table of FIG. 3, after a time of 1,30 and 240 minutes of being released from the load, being able toobserve how the sample of section 3 presents a recovery index of 100%already at 30 minutes of releasing the load.

In the same way, in FIG. 3 of the designs, the evolution of the recoveryindex is observed in the four analyzed samples at a fiber height of 60mm, so that once the stationary time (240 minutes) is reached, therecovery considerably increases arriving, in the samples object of theinvention, to said value.

In FIG. 4 of the designs, the classification of the result obtained fromthe four analyzed samples is depicted, being able to observe how thefibers of the sample 3 object of the invention are the ones that recovermore, having logically, higher resilience.

Lastly, in FIG. 5 of the designs the evolution of the recovery index ofthe four analyzed samples is depicted at a fiber height of 60 mm, beingable to observe how the sample 3 object of the invention is the onehaving a greater recovery index.

In this manner, it is concluded that a fiber 1 for forming carpets forartificial turf with a flat rectangular general cross section with itsshorter sides rounded, and in the central part of its longer facesprovided with a curved-convex projection 2, and in its other longer faceprovided with a pair of curved-convex projections 3 in a symmetricalposition with respect to its central axis, presents high resiliencemaking the fibers forming the artificial turf carpets to recover theirvertical position after being subjected to some successive compressiveloads and making them to maintain their original aesthetics over time.

In a preferred implementation of the fiber 1 for forming artificial turfcarpets, it has a width “D” of approximately 1400 μm.

On the other hand, the thickness “d” of the fiber for artificial turf inthe central part of the curved-convex projections is the same for all ofthem, such that in a preferred implementation is of approximately 270μm.

1. A fiber for artificial turf, being of the type of monofilament fibersutilized in the manufacturing of artificial turf carpets and which areobtained by extrusion in polyethylene or another material, the fibercomprising: a flat rectangular general cross section with shorter sidesthereof rounded; a central part of one of longer faces of the fibercomprising a curved-convex projection, and a second of the longer facescomprising a pair of curved-convex projections in a symmetrical positionwith respect to a central axis of the fiber.
 2. The fiber for artificialturf, according to claim 1, wherein the fiber forming the carpets forartificial turf has a height of approximately 60 mm.
 3. The fiber forartificial turf, according to claim 1, wherein the fiber forming thecarpets for artificial turf has a width of approximately 1400 μm.
 4. Thefiber for artificial turf, according to claim 1, wherein the thicknessof the fiber forming the carpets for artificial turf in the central partof the curved-convex projections is the same for all fibers in thecentral part.
 5. The fiber for artificial turf, according to claim 1,wherein the thickness of the fiber forming the carpets for artificialturf in the central part of the curved-convex projections is ofapproximately 270 μm.
 6. The fiber for artificial turf, according toclaim 4, wherein the thickness of the fiber forming the carpets forartificial turf in the central part of the curved-convex projections isof approximately 270 μm.